Apparatus for emitting vapors of volatile insecticidal agents or of similar volatile products

ABSTRACT

An apparatus which is adapted for emitting at room temperature vapors of volatile insecticidal agents or of similar volatile active liquid products such as insect repellants comprises a body made from a single fibrous plate or a stack of fibrous plates capable of absorbing the agent or product. The body is coated on at least one of its larger, principal outer faces with a diffusion layer of polymeric material diffusable by the said agent or product so as to emit vapors of the latter from the outer surface of the layer; the layer adheres on its inner side intimately to the fibers of the adjacent face of the fibrous plate to which it is applied. The apparatus further comprises a frame of metal or synthetic thermoplastic or the like material impervious to the volatile agent or product or to its vapors and sealing the body hermetically on all sides except the face or faces thereof which are coated with a diffusion layer where the frame has a window or windows; the layer is hermetically sealed along its periphery to the frame.

United States Pat ent [191 Rabussier et al.

[ APPARATUS FOR EMITTING VAPORS OF VOLATILE INSECTICIDAL AGENTS OR OF SIMILAR VOLATILE PRODUCTS [75] Inventors: Bernard Rabussier, Aventon;

Jean-Pierre Mandon, Poitiers;

Claude Hennart, Aubervilliers, all of France [73] Assignee: Ciba-Geigy AG, Basel, Switzerland [22] Filed: Feb. 18, 1972 [21] Appl. No.: 227,578

Related US. Application Data [63] Continuation-impart of Ser. No. 839,721, July 7,

1969, Pat. No. 3,698,974.

[52] US. Cl. 239/56, 239/57 [51] Int. Cl. A24f 25/00, A611 9/04 [58] Field of Search 239/5357 [56] References Cited UNITED STATES PATENTS 1,496,326 6/1924 Schulte 239/57 1,871,418 8/1932 McKee... 239/56 2,755,954 7/1956 Antritter 239/57 X 2,988,284 6/1961 Smith 239/55 X 3,087,679 4/1963 Wilson 239/57 3,129,888 4/1964 OHagan 239/55 3,216,882 11/1965 Feldt et al 239/54 X 3,426,473 2/1969 Cardarelli et a1. 239/53 X 1 Jan. 7, 1975 3,608,062 9/1971 Alfes et al 239/60 X 3,685,734 8/1972 Paciorek 239/54 X Primary Examiner-M. Henson Wood, Jr. Assistant Examiner-John J. Love Attorney, Agent, or FirmWend.eroth, Lind & Ponack [57] ABSTRACT An apparatus which is adapted for emitting at room temperature vapors of volatile insecticidal agents or of similar volatile active liquid products such as insect repellants comprises a body made from a single fibrous plate or a stack of fibrous plates capable of absorbing the agent or product. The body is coated on at least one of its larger, principal outer faces with a diffusion layer of polymeric material diffusable by the said agent or product so as to emit vapors of the latter from the outer surface of the layer; the layer adheres on its inner side intimately to the: fibers of the adjacent face of the fibrous plate to which it is applied. The apparatus further comprises a frame of metal or syn thetic thermoplastic or the like material impervious to the volatile agent or product or to its vapors and sealing the body hermetically on all sides except the face or faces thereof which are coated with a diffusion layer where the frame has a window or windows; the layer is hermetically sealed along its periphery to the frame.

19 Claims, 7 Drawing Figures APPARATUS FOR EMITTING VAPORS OF VOLATILE INSECTICIDAL AGENTS OR F SIMILAR VOLATILE PRODUCTS This application is a continuation-in-part of our pending patent application Ser. No. 839,721, filed an July 7, 1969 now US. Pat. No. 3,698,974.

The present invention concerns an apparatus which is adapted for emitting at room temperature vapors of an insecticidal agent or of a similar volatile active liquid product such as an insect repellant.

The apparatus according to the invention assures a prolonged diffusion and substantially constant discharge of at least one insecticidal agent or the like product; it can be stocked without alteration before use, and assures when put to use a longlasting action, e.g., a protection against insects, notably flies, mosquitoes and mites.

It has been found desirable to produce industrially devices which are permanent diffusers of insecticidal vapor, particularly where the latter is constituted by dimethyl dichlorovinyl phosphate (or DDVP). This phosphoric ester possesses remarkable insecticidal properties, particularly against flies in domestic quarters.

Compositions having a homogeneous structure have already been produced in which DDVP is used in the form of a solid solution in various substances to provide blocks, cakes or analogous masses (see, for example French Pat. No. 1,343,700). However, such compositions are often sensitive to heat, with consequent risk of partial fusion, which could lead to serious accidents when drops fall to the ground. Further, when the retention of the ODVP is not strong, there is always some exudation of the active material, even without a rise in temperature. If, in order to avoid this risk, one uses a solid mass with a strong retention for DDVP, the evaporation decreases rapidly with time, and the yield is poor since unused DDVP remains.

Evaporation devices having a heterogeneous structure are also known, consisting of a reservoir of liquid insecticide, preferably DDVP, which feeds a diffusing panel permeable to this agent, preferably of plasticised polyvinyl chloride or a thin sheet of polyethylene (see, for example, French Pat. No, 1,310,865). In evapora tors of this kind, the presence of a relatively large quantity of liquid DDVP in the reservoir involves serious risks of poisoning during storage, transport or use if the reservoir is inadequately sealed or deteriorates. This danger creates a serious problem in selecting material for the reservoir, and necessitates the provision of a protective exterior for the evaporate device which protects against deterioration of the reservoir and/or the diffusion panel.

The French Pat. No. 2,553,792 described evaporative devices in which an exterior diffusion panel penneable by DDVP consisting of a thin layer of a thermoplastic material such as polyethylene is applied to a substance containing DDVP in the form of a solid solution in a thermoplastic material. The methods for producing such evaporators are of two types:

a. the exterior diffusion panel is a film, separated from the substance containing the insecticide;

b. the exterior diffusion panel is a laminated product attached to the substance containin the insecticide.

The evaporators made according to process (a) have the drawback that they require a relatively large evaporation surface for two reasons:

1. it is very difficult to use industrially very thin plastic panels without also providing a support;

2. the transmission of DDVP between the solid solution and the exterior diffusion panel is bad due to the non-adherence of these two elements.

Moreover, the method of type (b) involves great technological difficulties, for it is very difficult to bring about satisfactory close adherence between a thin film of polymer with a mass of another polymer continuously diffusing gas or extruding liquid.

The apparatus according to our invention which is adapted for emitting at room temperature vapors of a volatile active liquid product, comprises (a) an evaporator unit consisting essentially of:

i. a plate body consisting of at least one fibrous product-absorbing plate;

ii. diffusion layer of polymeric material capable of permitting said product to diffuse therethrough and vapors of said product to evaporate from an outer surface thereof at an effective rate, said layer being superimposed on at least one of the two larger, principal outer faces of said plate body, and being intimately joined with its inner face to the adjacent large principal surface of said plate body; and

iii. a frame made of a material preferably selected from metal and synthetic thermoplastic material and being impervious to said liquid product and the vapors of the latter, and having at least one window registering with an aforesaid diffusion layer and being sealingly connected by means of at least a marginal frame portion about said window to the underlying peripheral zone of said diffusion layer, said vapor-impervious frame hermetically enclosing said body on all sides of the latter which are free from a diffusion layer;

b. as well as: protective means impervious to said liquid product and vapors thereof, and adapted to sealing in said apparatus after absorption of active liquid product u said in body.

The fibrous product-absorbing material from which the said plates are made is in practice selected from strong-sized paper, non-sized paper, wool felt, felt card, cardboard, glass fiber and non-woven fabric. Paper and cardboard are preferred on account of their good stability and absorptivity for the voflatile active liquid.

In practice, the frame is usually equipped with a sealable filling means].

The apparatus according to the invention is designed for the emission of vapors of volatile active liquid products, and in particular of insecticidal substances, especially of phosphoric acid esters such as dimethyl dichlorovinyl phosphate (DDVP).

The method of manufacturing such apparatus comprises the impregnation of a single fibrous absorbant plate or at least one such plate in a stack containing several thereof, with the product or an agent which can be a pure active, e.g., insecticidal substance, or a solution of the latter.

The frame is preferably of several structural elements held together by a system of joints between them. A protective packing of the device for storage before use is also envisaged.

The diffusion layer is advantageously constituted by a thin film of plastic material such as polyethylene, polypropylene or a copolymer with a high content of vinylidene chloride.

Preferably, the fibrous mass is constituted by an ab- I sorbent plate formed of agglomerated fibres, while the product is preferably a solution of volatile phosphoric ester in a non-volatile hydrophobic diluent such as a dialkyl phthalate.

A general process of industrial manufacture of the apparatus according to the invention includes the following operations:

1 -a. coating, preferably in a continuous process, at least one principal face of a fibrous absorbent plate with a thin layer of polymeric material destined to act as diffusion layer, followed by cutting the coated fibrous plate into plates of any desired shape or size and, if desired, forming a stack from two plates only the outer surfaces of each of which bear a diffusion layer, or from more plates by interposing intermediate uncoated plates between the two aforementioned plates being the outer ones of the stack.

1 b. mounting a flexible or rigid frame of thermoplastic material or metal having a window for each diffusion layer present in the plate or stack to be enclosed, about the said plate or stack and sealing the frame with the edge portion about each window to the periphery of each diffusion layer present in the plate or stack, the frame hermetically enclosing the plate or stack on all sides thereof free from a diffusion layer.

When a stack of several plates is formed, the two outer ones of which bear each a diffusion layer on its outer face, the frame can consist of two elements each of which has a window and is sealed by the marginal portions surrounding the window to the periphery of the diffusion layer of one of the plates, whereupon the two open sides of the frame elements opposite the side thereof fastened to a diffusion layer are joined hermetically together, e.g., by welding or the like known procedure.

1 -c. covering each window by a mechanically removable protective sheet or foil impervious to the agent or product and to its vapors and sealing the edges of the protective sheet on to the frame portions about said window;

1 d. drying of the unit obtained according to l-(b), and

1 e. impregnating the plate or stack in the unit with the volatile agent or product, or a solution thereof in a non-volatile solvent, introducing the same through the sealable filling means and sealing the latter. Preferably, operations 1(a) to 1-(e) are carried out in a dry atmosphere, and when manual movements are necessary for these operations they should be made in a protective enclosure such as a glove-box.

In certain variants of this general procedure, the

order of different operations can be changed in a suitable manner.

We will now describe in detail the characteristics of the constituent elements necessary for the evaporation apparatus.

The substance constituting the absorbent fibrous plate must have a good absorbent capacity and good power of retention for the chosen volatile product, e.g., an insecticide such as DDVP with respect to which it of be inert. Furthermore, the absorbent plate should not contain impurities likely to react with the insecticide or other product and must be capable of easy dehydration.

In view of the above, the absorbent plate is constituted preferably by one of the following substances: a strong non-sized paper, a card of non-sized cellulose, a wool felt, a felt card, a cardboard or old papers, a pack of glass fiber, a felt of glass fiber or a non-woven fabric.

The thin layer, of polymeric material consists preferably of one of the following substances: a polyethylene, a polypropylene, a mixture of polyethylene and polypropylene, a copolymer of ethylene and propylene, or a copolymer with a high content of vinylidenechloride. When a copolymer of vinylidenechloride is used its content of vinylidenechloride is generally between and 97 percent and preferably between 87 and 95 percent. The monomer copolymerised with vinylidene chloride in these copolymers can be in particular vinylchloride, an acrylic ester or acrylonitrile.

The diffusion layer does not have micropores which, if they existed, would lead to a permeability by flow, thus being non-selective. The slow passage of the volatile product, e.g. DDVP occurs by activated diffusion, that is to say, by a movement molecule by molecule from one free space to another, with substantial interaction between the membrane and the diffusing molecules. The quantity of product traversing the membrane per unit of time increases with an increase in the temperature, and the diffusion is selective. The diffusion of the diluent is practically nil, and the absorption of humidity is very weak, even though a product like DDVP is hydroscopic.

The thickness of the diffusion layer should be generally between 10 and microns, and preferably between 20 and 40 microns.

The frame, when of thermoplastic substance, can be either flexible, semi-rigid or rigid. In the case of a flexible frame it is preferably cut out of a sheet of thermoplastic substance of the same nature as that of the diffusion layer but having a thickness that is from 4 to 20 times as great. In the case of a semi-rigid or rigid frame, it is preferably obtained by moulding from a thennoplastic substance of the same nature as the diffusion layer. The rigidity of the frames obtained by molding depends on their shape and thickness. Frames obtained by molding are advantageously equipped with bars constituting a grille across the window or windows for the protection of the evaporation surfaces. This grille prevents contact with the evaporation surfaces, and prevents young children from tearing or licking them.

When an insecticide is to be used for impregnating the fibrous absorbent plate, it is preferably a liquid volatile phosphoric ester, such as DDVP; in any case, the DDVP or another active substance used should be as pure as possible, and at least of a purity of percent. Its acidity should be as weak as possible. The active agent is advantageously in solution in a non-volatile hydrophobic diluent. This should not be susceptible to reaction with DDVP or the like product, nor provoke its decomposition over a period of time. It should be liquid at ordinary temperature. It should be miscible with DDVP or another active product at ordinary temperature and at the concentration required for use. Preferably, the vapor tension of the diluent at 20C should be less than 0.03 mm of mercury.

The quantity of the insecticide or other volatile product supplied to each apparatus depends on the nature of the volatile agent or product, the space to be treated, the length of time for which it is required and the residual amount of the volatile agent or product retained in the fibrous absorbent plate. The quantity is, for instance, about to 25 g of DDVP for an apparatus intended for a space of 30 m for a period of three months.

The impervious protective sheet is preferably of a thermoplastic material of the same nature as that of the frame, with sufficient thickness (for example 0.5 mm in the case of high density polyethylene) to ensure that the diffusion of volatile product, e.g., the phosphoric ester will be negligible during storage. Preferably the impervious sheet is made from a laminate, heatsealable on one face, of the type known in the packing field as a complex. The complexes known are very numerous; the number and nature of their layers vary. One finds in different complexes the following layers: paper, aluminum, low-density polyethylene, highdensity polyethylene, polyamide, polyester, copolymer of vinylidene acetate of cellulose, etc. lt is necessary to choose a complex the layers of which will not delaminate on contact with the vapours of the phosphoric ester or other volatile product, and it is preferable to choose a complex the internal layer of which is made of a thermoplastic substance of the same nature as the frame of the apparatus.

The deposition and intimate adherence of the diffusion layer on the fibrous absorbant plate can be achieved, preferably in a continuous process, by methods known and used in the industrial manufacture of papers and packaging cartons coated with a layer of plastic substance. The deposition can be made in one or more successive layers (or coats). In the case of polyethylene, the deposition can be effected either by the technique known as extrusion-lamination, or by coating with an aqueous or organic dispersion of very fine polyethylene powder; this last technique, described by McSHARRY, HOWELL and MENERING in Plastiques Modernes et Elastomeres, April 1968, has the advantage of giving a highly superior bonding of the polyethylene and the absorbent plate. In the case of vinylidene copolymer, the deposit can be preferably obtained by coating from an aqueous dispersion. One can also use a solution of the plastic substance in a volatile solvent which is uniformly sprayed on one of the faces of the plate. The adherent deposit can also be obtained by sticking that is to say by heat-lamination of a film on the fibrous plate.

The cutting of plates is carried out by known methods, for example with a paper-cutter for square and rectangular forms or with a punch-press for the other shapes.

The sealing along the periphery of the coated face of the plates on the frame of thermoplastic material is ef fected over a width of about 2 to 5 mm by thermic or heat seal with the aid of a metal heating block of the same shape as the absorbent plate. The temperature of the heating block depends on the nature and thickness of the thermoplastic substance. This temperature should be controllable to a precise degree. Further, the heating block should exert a certain pressure between the pack of absorbent plates and the diffusion layer or layers and the frame in order to assure hermetic sealing; this pressure should be controllable to a precise degree, and to this end the movement ofthe heating block is preferably controlled by a pneumatically driven screw with a delay mechanism. When theframe is a flexible frame, that is, a fairly thin frame, the heating block is applied to the frame. When the frame is a rigid frame, that is, a relatively thick one, the heating block is applied to the non-coated face of the plate or pack of plates, the heat necessary for the fusion of the marginal portions of the diffusion layer being transmitted through the fibrous plate.

The dessication of the plate or pack when mounted in the frame is carried out by known methods, for example by submitting the pieces to infra-red rays in a tunnel, taking care to turn the non-coated face of the plate or pack of plates towards the rays. The temperature in the dessication zone should. be regulated in such a way that it does not induce a permanent deterioration or deformation of the thermoplastic parts. The duration of time in the dessication zone depends on the temperature in the cavity and on the degree of humidity in the fibrous plate.

The impregnation of the fibrous plates, coated and mounted in a frame element, which leaves the uncoated face of the plate free, with the volatile product, e.g., the phosphoric ester, pure or in solution, is effected, preferably, by distribution of the liquid by the use of a dosage means on the plates, while the latter is in a horizontal position. The speed of distribution should be regulated according to the speed of absorption of the liquid by the plate, so that the liquid does not soil the frame.

The junction of the frame elements of two plates impregnated as described above, or of two plates prior to impregnation, is effected by a sealing method which differs depending on whether it is a flexible frame, with a relatively small thickness; or a rigid frame which is relatively thick.

When the frame is a flexible frame the junction is made over a width of about 2 to 5 mm by heat sealing between two heating blocks similar to one another, the blocks forming a grip or pincer. the shape of which corresponds to that of the frame. The two heating blocks are either metallic blocks similar to those used for the sealing of the diffusion layer to the frame, or rigid armatures furnished with a heating ribbon. The temperature, the time and the pressure of the pincer grip, and the cooling time while keeping the frames under pressure when a heating ribbon device is used are determined by the nature and thickness of the thermoplastic material of the flexible frame. The: joining of the flexible frames can also be effected by heat welding by the use of a heating wire.

In the case of a rigid frame the junction is made over a width of 1 to 3 mm (approx.) preferably by a proce dure known by the name of heated tool welding.

The sealing of the impervious protection sheet on the frame is effected over a width of about 11 to 10 mm preferably by the heat welding, with the use of a metallic heating block similar to that used for the sealing of the coated plates onto the frames. When the impervious sheet is a complex including a sheet of aluminum, one can also use a high-frequency solder technique using the heat energy developed by a highfrequency current.

In certain other variations of procedure, well-known soldering techniques, different from those described in the details of the assembly operations can be used.

There are described hereinafter certain variants of the constituent elements of the apparatus according to the invention; these variants can be used singly or in combination with others:

2 a. the frame has an orifice, a ring, an autoadhesive surface or any other means for causing the diffuser to be attached;

2 b. when the frame is rigid or semi-rigid it has feet or any other means for maintaining the diffuser in a vertical position on a horizontal surface.

2 c. The capacity of absorption in the emission apparatus for phosphoric ester or similar products, pure or in solution, is increased by the insertion in a pack of one or more uncoated plates of absorbent material between two absorbent fibrous plates coated on their outer faces. The inserted plates can be of the same or of a different material as the coated ones.

2 d. Only one fibrous absorbent plate is used, which plate is relatively thick and coated on both sides instead of the assembly of two plates each coated only on one side.

2 e. Only one fibrous absorbent plate is used, which plate is coated only on one side, the apparatus only diffusing from one side. In this case the assembly has only one frame having only one window.

2 f. In the case of a single diffusion layer the nondiffusing surface of the assembly can consist of a watertight reservoir, preferably moulded from a thermoplastic substance of the same nature as that of the frame supporting the diffusion layer. It can be integral with the frame or a separate element.

2 g. Two absorbent plates each of which has a large surface coated by a diffusion layer are juxtaposed with their uncoated large faces toward each other and are pressed together.

2 h. The frame is metallic, for example of galvanised hoop iron or aluminum, and coated with anticorrosive varnish on the inside. The following variants of the general procedure can be used singly or in combination:

3 a. The adherent coating of polymeric material (diffusion layer) is deposited on a thin sheet of nonabsorbent paper, non-woven fabric or similar material instead of being deposited on a fibrous absorbent sheet. One cuts this thin coated plate to the required shape. By the application of pressure, with heat, the coated face of the thin sheet is made to adhere to a fibrous absorbent non-coated plate previously cut to a slightly smaller size, so that the thin coated sheet projects beyond the perimeter of the fibrous absorbent plate. Impregnation is carried out, then the two coated elements are joined in such a way that the two fibrous surfaces are positioned one against the other. The edges of the two elements are then sealed, due to the presence of the coating of polymeric material. Thus there is produced a watertight assembly without a frame.

3 b. The thermoplastic frame seals the edges of the plate or the stack of plates and is applied by treating the edges with a thick coating of thermoplastic material in the form of a concentrated solution, which is then dried, or a coating of melted thermoplastic substance which is then solidified by cooling.

3 c. When the absorption capacity is increased by inserted absorbent plates [case 2(c)] these plates can be held on the coated plates by one or several spots of glue to facilitate the subsequent operations in the manufacture.

3 d. When a single fibrous absorbent plate coated on one or both sides is used [variants 2-(d) or 2(e)], the active liquid product is injected into the absorbent fibrous mass by the use of a hollow needle introduced into the edge of the plate.

3 e. In the case of a flexible frame the joining of the frames can be effected by partial sealing before impregnation, thus forming a kind of sachet with an opening through which can be introduced the active liquid between the two fibrous absorbent plates. The frames are then finally closed.

3 f. In the case of semi-rigid or rigid frames of thermoplastic material, the frames are joined by sealing before impregnation. A hole is made in the side of the frames and the active liquid is injected between the two fibrous absorbent plates by means of a hollow needle inserted through the hole. Then the hole is stopped up by fusion of the thermoplastic material, possibly with the addition of a little more of the material.

3 g. When the absorption capacity is increased by providing inserted absorbent plates [variant 2(c)] impregnation is limited to these plates, and is effected by dipping them into the active liquid product just prior to introduction into the stack.

3 h. When the frame is metallic [variant 2-(h)] it is sealed hermetically on the diffusion layer by crimping in lieu of heat-welding.

3 i. In a case where one of the diffusion surfaces is replaced by a watertight reservoir [variant 2(f)] the active solution is introduced directly into the reservoir, which then receives the coated fibrous absorbent plate and is mounted in its frame.

3 j. In the case where the active solution is absorbed or gelatinized [variant 2-(g)] impregnation is effected by the deposition of a paste or cream on the absorbent fibrous plate. The diffusion of the active solution into the fibrous absorbent plate occurs slowly and of its own accord after the frames have been sealed.

3 k. Instead of impervious sheets sealed on to the frame an impervious envelope, e.g., a sachet having thermosealed edges encloses the plate or stack of plates into which the active liquid product has been introduced.

3 1. Instead of impervious sheets sealed on to the frame an airtight metallic box is used, designed to be opened by hand, for example, a system known as TIR- HOP. In the accompanying drawings, various embodiments of an evaporator unit to be used in apparatus according to the invention have been illustrated; however, in several of the figures, a protective envelope or protective sheets impervious to the vapors of the active product which are to emanate from the diffusion layer or layers of the units have been omitted for the sake of clarity.

In the drawings:

FIG. 1 shows a first embodiment of an apparatus according to the invention inclusive of the evaporator unit, in a schematic perspective partially sectional view;

FIG. 2 shows, in a view similar to that of FIG. 1, a second embodiment of the evaporator unit according to the invention, protective sheets or a protective envelope having been omitted;

FIG. 3 shows in a similar view a third embodiment of the evaporator unit;

FIG. 4 shows in a similar view a fourth embodiment of the evaporator unit;

FIG. 5 shows in a similar view a special embodiment of the evaporator unit in which the frame of the unit is integral with the diffusion layer thereof;

FIG. 6 shows in an elevational view another embodiment of apparatus according to the invention, from the top side of which a protective sheet has been removed, and

FIG. 7 shows a cross sectional view of the same apparatus, taken along line VII-VII in FIG. 6.

The evaporator unit of the apparatus illustrated in FIG. I is produced in conformity with the variants 2(e) and 3-(b) and active liquid product can be introduced by method varient 3(d). In this figure, the reference numeral 1 designates a single fibrous absorbent plate, of rectangular shape, of which one large sur face is coated with a diffusion layer 2 the inner side of which adheres intimately to the fibrous adjacent surface of the plate 1. The opposite large surface of plate 1 is covered by a vapor-impervious sheet 3' of thermoplastic material. The block sandwich thus constituted is sealed by a frame 3 of a thermoplastic substance and of a thickness rendering it vapor-impervious, which frame is welded, glued or pressed on to the peripheral edges of layer 2 and sheet 3.

The evaporator unit shown in FIG. 2 is in conformity with the method variants 2(g) and 3--(b). In this figure, 1a and 1b are fibrous absorbent plates of rectangu lar shape, juxtaposed and pressed against one another.

Each absorbent plate has the outwardly facing surface covered by a diffusion layer 2a, 2b, respectively which adheres intimately thereto. The block thus constituted is sealed by a frame 3 of thermoplastic material.

The evaporator unit of FIG. 3 is similar to that of FIG. ll, but made according to the method variants 2(a), 2(d), 2(h) and 3-(h); active liquid product can be introduced in accordance with method variant 3-(d).

In FIG. 3, the fibrous absorbent plate 1 has a rectangular shape; its two large surfaces are covered by two diffusion layers 2 which adhere intimately thereto. The mounting consists of a metallic frame 3a the edges 4 of which are crimped to provide a sealing grip on the periphery of the diffusion layers 2. The frame 3a is equipped with an apertured tab 5 and bosses 6, designed to maintain the layer 2 facing the wall at which the apparatus is suspended, at a certain distance therefrom to allow the free circulation of air and permit good diffusion of the active product vapors.

FIG. 4 illustrates another embodiment made according to variant 2(c). In this figure, la and lie are fibrous absorbent plates, rectangular in shape, the outwardly facing surfaces of which are covered by diffusion layers 2a and 2b, respectively, llb is an uncoated absorbent plate inserted between plates la and 110. Two frame elements 3a and 3b of thermoplastic material are sealingly connected on the inside of their rims 4a and 4b to the peripheral zones on the outer faces of diffusion layers 2a and 2b, respectively. They are welded together by the weld 3c. The resulting frame holds the three sheets pressed together. Two imperious protective sheets a sheet 5a and a similar sheet not visible in the drawing, are soldered on to the outside of the rims 4a and 4b of frame elements 3a and 3b.

FIG. 5 illustrates another evaporation unit made according to variant 3-(a). In this figure, la and lb are fibrous absorbent plates rectangular in shape on which the polymer-treated surfaces 2a and 2b of sheets of paper 7a, and 7b, impervious to vapors of the active liquid product, have been stuck by applying pressure and heat. These paper sheets 7a and 7b have dimensions slightly larger than those of the fibrous absorbent plate la. After impregnation, the two semiassemblages la-2a-7a and 1b2b7b are joined by heat soldering about the whole perimeter ill) the contact margin of the coated paper sheets 7a and 7b. This vapor emission apparatus thus comprises two impervious sheets of paper 7a and 7b as exterior surfaces the marginal portions of which, together with weld 10 form the frame of the apparatus. In order to put this apparatus in operation, it is necessary to cut or tear off a portion of the paper sheets 7a or 7b.

FIG. 6 is a view in elevation of a particular industrial version of the apparatus according to the invention made according to variants 2(c) and 3-(g).

In FIG. 7 the edge of two fibrous absorbent plates Ia and lb, together with their respective diffusion layers 2a, 2b, are lodged in groove 9 of the two half frames 8a and 8b which are to be joined one to the other along the rims 9a and 9b along groove 9 and which project from half frames 8a and 9b. The surface of the diffusion layer 2a, 2b is soldered on the periphery to the contact surface of groove 9. Plate 10 of fibrous material impregnated with the active liquid product is placed between the two plates la-2a and llb-2b before enclosing the stack between the two half frames 8a, 8b and welding the latter together. The two half frames 8a, 8b are advantageously made of thermoplastic material (for ex ample, of polyethylene) and the inner rim portions 12a and l2b serve as supports for the molded crossed bars 11 constituting protective grilles situated at a relatively great distance from the diffusion layers 2a and 2b.

This arrangement avoids any accidental contact with surfaces 2a, 2b, and prevents children from tearing or licking them. At the same time, the two half frames having their rims 9a and 9b sealed together hold the elements of the apparatus in firm assembly and give the apparatus rigidity.

After some days storage the active liquid product initially contained in the plate Ic has spread uniformly by capillary action among the three fibrous plates Ia, llc, and lb.

Good preservation in storage is ensured by sealing the edges of impervious sheets B3 on to the edge of the frame, as at Ma and lllb.

At the time of use the impervious sheets are easily cut by continuous perforation if these have been formed for this purpose in the two lateral faces of the frame grooves 11a and Mb.

The emission apparatus according to the invention has the following notable advantages:

long duration of action (1 to 6 months) regularity of evaporation with time good storage quality before and during use safety during storage, transport and use low cost.

This combination of advantages is peculiar to the combination of methods envisaged by the invention.

There will now be described two detailed examples of a diffusion apparatus and the results obtained from tests of these embodiments:

A. Diffusion apparatus of FIG. 4:

a. coated plate la or lcGrey card made of old papers having a weight of 560 g/m with a coating of 45 g/m of polyethylene. Square format 14x14 cm.

b. intermediate plate lbCellulose card, unsized, 1000 glm Square format l4 l4 cm.

c. Active solution DDVP, technical at 96% 76% dioctyl phthalate 20% epoxidised soya oil 4% Total quantity impregnated into the three plates: 51 g, that is g on the intermediate plate and 8 grammes on each coated plate.

d. Assembly The diffusion layers 2 are soldered at their edges on to the interior surface of the rim 4 of the two frames of polyethylene 3a, 3b, of 2 mm thickness.

The two frames, 3a, and 3b, are soldered to each other by heated tool welding in at 3c. The two impervious sheets, 5a and the sheet not visible are soldered on the exterior surface of the rim 4.

Put into service in a room at 22C this diffusion apparatus emits the insecticidal vapors of DDVP at a constant level of about 100 mg/day for 130 days. At the end of 65 days of emission the diffuser is placed in a closed chamber of 30 m free from all products of insecticidal action. The temperature of the room is 25C and the hygrometric degree is 40 percent. As soon as the diffuser has been put into the room, 100 domestic flies (Musca domestica) are introduced. At the end of 49 minutes it is noted that half these flies are in decubitus dorsal. The figure is 87 percent at the end of an hour.

B. Diffusion apparatus of FIG. 5:

a. Coated paper 2a, 7a or 2b, 7b Bleached kraft paper 40 g/m Coating of copolymer of vinylidene in an amount of g/m in two layers Square format l2 12 cm.

b. Absorbent plate la or lbCellulose card, nonsized,

1,000 g/m Square format l0 1O cm.

c. Active solution DDVP, technical 96% 76% Dioctyl phthalate 20% Epoxidised soya oil 4% Total quantity impregnated into the two plates: g.

Put into service in a room at 22C, this diffusion apparatus emits insecticidal vapors of DDVP at a constant level of 175 mg/day (approx.) for to days. Emission at 60 days is still 125 mg/day. At the end of days of diffusion the diffuser is placed in a closed room of 30 in free from all products with insecticidal action. The temperature of the room is 25C and the hygrometric degree is 35 percent. Immediately after putting the diffuser in the room, 100 flies (Musca domestica) are introduced. It is noted that half the flies are in decubitus dorsal after 28 minutes. The mortality is total at the end of minutes. The same biological tests after days of evaporation gives a decubitus dorsal of 50 percent in 30 minutes and 98 percent at the end of an hour.

If one takes as the limit of useful employment the time when the level of evaporation of insecticide is no more than 70 percent of the initial level, the balance sheet of the active material is as follows in the case of DDVP:

DDVP regularly diffused: 65 to DDVP hydrolised in plates of fibrous material 5 to 15% DVVP remaining in the plates of fibrous material 10 to 30% The duration and consistency of insecticidal effect are, in the two cases, particularly remarkable when one considers the simplicity and the low cost of the means employed.

We claim:

1. An apparatus adapted for emitting at room temperature vapors of a volatile active liquid product, comprising a. an evaporator unit consisting essentially of a. a plate body having two large end faces at opposite sides thereof and comprising i. at least one fibrous product absorbing plate;

and

a diffusion layer of thermoplastic polymeric material 10 to u thick capable of permitting said product to diffuse therethrough and vapors of said product to evaporate from an outer surface thereof at an effective rate, said layer being superimposed on at least one of the two larger, principal outer faces of said plate body, and being intimately joined with its inner face to the adjacent large principal surface of said plate body; and b. a frame made of a material selected from metal and synthetic thermoplastic material, being impervious to said liquid product and the vapors of the latter, and having at least one window registering with an aforesaid diffusion layer and being sealingly connected by means of at least a marginal frame portion about said window to the underlying peripheral zone of said diffusion layer, said vapor-impervious frame hermetically enclosing said body on all sides of the latter which are free from a diffusion layer; and B. openable or removable protective means impervious to said liquid product and vapors thereof and adapted for scaling in said apparatus'after absorption of active liquid product in said plate body.

2. An apparatus as described in claim 1, wherein said protective means comprise a sheet the periphery of which is sealed hermetically to said frame so as to cover a window therein.

3. An apparatus as described in claim 1, wherein said protective means comprise an impervious openable envelope sealingly enclosing said evaporator unit, thereby preventing loss of vapors of said active liquid product during storage of said apparatus.

4. An apparatus as claimed in claim 1 in which the diffusion layer has as the main constituent thereof a material selected from the group consisting of polyethylene, polypropylene, a mixture of polyethylene and polypropylene, a copolymer of ethylene and propylene, a copolymer of vinylidene chloride with vinyl chloride, a copolymer of vinylidene chloride with an acrylic ester, and a copolymer of vinylidene chloride with acrylonitrile having a vinylidene chloride content of from about 75 to 97 percent calculated on the total weight of the copolymer.

5. An apparatus as claimed in claim 1 in which the frame and the diffusion layer are of identical polymeric material.

6. An apparatus as claimed in claim 1 wherein said plate body comprises a plurality of face-to-face fibrous absorbent plates therein and a volatile active liquid product impregnating said absorbent plates.

7. An evaporator unit for use in apparatus adapted for emitting at room temperature vapors of a volatile active liquid product, comprising a. a plate body which comprises i. at least one fibrous product-absorbing plate; and

ii. a diffusion layer of thermoplastic polymeric material to 80p. thick capable of permitting said product to diffuse therethrough and vapors of said product to evaporate from an outer surface thereof at an effective rate, said layer being superimposed on at least one of the two larger, principal outer faces of said plate body, and being intimately joined with its inner face to the adjacent large principal surface of said plate body; and

b. a frame made of a material being impervious to said liquid product and the vapors of the latter, and having at least one window registering with an aforesaid diffusion layer and being sealingly connected by means of at least a marginal frame por tion about said window to the underlying peripheral zone of said diffusion layer, said vaporimpervious frame hermetically enclosing said body on all sides of the latter which are free from a diffusion layer.

8. An evaporator unit as described in claim 7, wherein said frame is made of metal and is crimped about the rim of said plate body, thus being hermetically sealed to the diffusion layer.

9. An evaporator unit as described in claim 7 wherein said fibrous product-absorbing plate is of a material selected from strong-sized paper, non-sized paper, wool felt, felt card, cardboard, glass fiber and non-woven fabric.

10. An evaporator unit as described in claim 7, wherein said plate body consists essentially of a single fibrous product-absorbing plate.

11. An evaporator unit as described in claim 10, wherein said single fibrous product-absorbing plate bears an aforesaid diffusion layer only on one of its large faces.

12. An evaporator unit as described in claim 7, wherein said plate body comprises two fibrous productabsorbing plates each of which bears an aforesaid diffusion layer on one of its two large faces, said two plates being juxtaposed with their two uncoated large faces, said two diffusion layers being opposite end faces of said plate body.

13. An evaporator unit as described in claim 12,

wherein said two plates are joined together with their respective large uncoated faces.

14. An evaporator unit as described in claim 12, wherein said plate body comprises at least one fibrous absorbent plate free from a diffusion layer interposed with its two large faces between and in direct contact with the uncoated large faces of said two end plates.

15. An evaporator unit as described in claim 12, wherein said frame consists of two half boxes each of which has a window containing a grille, and each of which is mounted about one of said terminal end plates with the window and grille therein spacedly above the diffusion layer of said end plate, and wherein each of said half boxes has a rim disposed about the periphery of the respective end plate and extending beyond the latter toward the other end plate, the rims of both half boxes being sealingly connected with each other.

16. An evaporator unit as described in claim 15, further comprising protective means comprising two sheets of vapor-impervious material, each of said sheets being sealingly connected to the marginal zones of one of said half boxes about and above said window and grille therein.

17. An evaporator unit as described in claim 7, wherein said frame is made of said impervious thermoplastic material.

18. An evaporator unit as described in claim 7, wherein said diffusion layer is made of a thermoplastic polymeric material selected from polyethylene, polypropylene and plasticized polyvinyl chloride.

19. An evaporator adapted for emitting at room temperature vapors of a volatile active liquid product, comprising a. a plate body having two large end faces at opposite sides thereof and comprising i. at least one fibrous product-absorbing plate and ii. two diffusion layers of polymeric thermoplastic material 10 to t thick capable of permitting said product to diffuse therethrough and vapors of said product to evaporate from an outer surface thereof at an effective rate, one of said layers being superimposed on each of said large, principal end faces of said plate body and being intimately joined with its inner face to the adjacent surface of said plate body; each diffusion layer having a marginal portion which extends beyond said plate, the two marginal portions of said diffusion layers being sealed together to form a frame about said plate body b. protective enveloping means of a material impervious to said liquid product and to the vapors of the latter, said protective means being of foil-shape and tearably and removably laminated on to the outer surface of each of said diffusion layer.

l= =l= =l 

1. An apparatus adapted for emitting at room temperature vapors of a volatile active liquid product, comprising Alpha . an evaporator unit consisting essentially of a. a plate body having two large end faces at opposite sides thereof and comprising i. at least one fibrous product absorbing plate; and ii. a diffusion layer of thermoplastic polymeric material 10 to 80 Mu thick capable of permitting said product to diffuse therethrough and vapors of said product to evaporate from an outer surface thereof at an effective rate, said layer being superimposed on at least one of the two larger, principal outer faces of said plate body, and being intimately joined with its inner face to the adjacent large principal surface of said plate body; and b. a frame made of a material selected from metal and synthetic thermoplastic material, being impervious to said liquid product and the vapors of the latter, and having at least one window registering with an aforesaid diffusion layer and being sealingly connected by means of at least a marginal frame portion about said window to the underlying peripheral zone of said diffusion layer, said vapor-impervious frame hermetically enclosing said body on all sides of the latter which are free from a diffusion layer; and Beta . openable or removable protective means impervious to said liquid product and vapors thereof and adapted for sealing in said apparatus after absorption of active liquid product in said plate body.
 1. AT LEAST ONE FIBROUS PRODUCT ABSORBING PLATE; AND II. A DIFFUSION LAYER OF THERMOPLASTIC POLYMERIC MATERIAL 10 TO 80 U THICK CAPABLE OF PERMITTING SAID PRODUCT TO DIFFUSE THERETHROUGH AND VAPORS OF SAID PRODUCT TO EVAPORATE FROM AN OUTER SURFACE THEREOF AT AN EFFECTIVE RATE, SAID LAYER BEING SUPERIMPOSED ON AT LEAST ONE OF THE TWO LARGER, PRINCIPAL OUTER FACES OF SAID PLATE BODY, AND BEING INTIMATELY JOINED WITH ITS INNER FACE TO THE ADJACENT LARGE PRINCIPAL SURFACE OF SAID PLATE BODY; AND B. A FRAME MADE OF A MATERIAL SELECTED FROM METAL AND SYNTHETIC THERMPOLASTIC MATERIAL, BEING IMPERVIOUS TO SAID LIQUID PRODUCT AND THE VAPORS OF THE LATTER, AND
 1. AN APPARATUS ADAPTED FOR EMITTING AT ROOM TEMPERATURE VAPORS OF A VOLATILE ACTIVE LIQUID PRODUCT, COMPRISING A. AN EVAPORATOR UNIT CONSISTING ESSENTIALLY OF A. A PLATE BODY HAVING TWO LARGE END FACES AT OPPOSITE SIDES THEREOF AND COMPRISING
 2. An apparatus as described in claim 1, wherein said protective means comprise a sheet the periphery of which is sealed hermetically to said frame so as to cover a window therein.
 3. An apparatus as described in claim 1, wherein said protective means comprise an impervious openable envelope sealingly enclosing said evaporator unit, thereby preventing loss of vapors of said active liquid product during storage of said apparatus.
 4. An apparatus as claimed in claim 1 in which the diffusion layer has as the main constituent thereof a material selected from the group consisting of polyethylene, polypropylene, a mixture of polyethylene and polypropylene, a copolymer of ethylene and propylene, a copolymer of vinylidene chloride with vinyl chloride, a copolymer of vinylidene chloride with an acrylic ester, and a copolymer of vinylidene chloride with acrylonitrile having a vinylidene chloride content of from about 75 to 97 percent calculated on the total weight of the copolymer.
 5. An apparatus as claimed in claim 1 in which the frame and the diffusion layer are of identical polymeric material.
 6. An apparatus as claimed in claim 1 wherein said plate body comprises a plurality of face-to-face fibrous absorbent plates therein and a volatile active liquid product impregnating said absorbent plates.
 7. An evaporator unit for use in apparatus adapted for emitting at room temperature vapors of a volatile active liquid product, comprising a. a plate body which comprises i. at least one fibrous product-absorbing plate; and ii. a diffusion layer of thermoplastic polymeric material 10 to 80 Mu thick capable of permitting said product to diffuse therethrough and vapors of said product to evaporate from an outer surface thereof at an effective rate, said layer being superimposed on at least one of the two larger, principal outer faces of said plate body, and being intimately joined with its inner face to the adjacent large principal surface of said plate body; and b. a frame made of a material being impervious to said liquid product and the vapors of the latter, and having at least one window registering with an aforesaid diffusion layer and being sealingly connected by means of at least a marginal frame portion about said window to the underlying peripheral zone of said diffusion layer, said vapor-impervious frame hermetically enclosing said body on all sides of the latter which are free from a diffusion layer.
 8. An evaporator unit as described in claim 7, wherein said frame is made of metal and is crimped about the rim of said plate body, thus being hermetically sealed to the diffusion layer.
 9. An evaporator unit as described in claim 7 wherein said fibrous product-absorbing plate is of a material selected from strong-sized paper, non-sized paper, wool felt, felt card, cardboard, glass fiber and non-woven fabric.
 10. An evaporator unit as described in claim 7, wherein said plate body consists essentially of a single fibrous product-absorbing plate.
 11. An evaporator unit as described in claim 10, wherein said single fibrous product-absorbing plate bears an aforesaid diffusion layer only on one of its large faces.
 12. An evaporator unit as described in claim 7, wherein said plate body comprises two fibrous product-absorbing plates each of which bears an aforesaid diffusion layer on one of its two large faces, said two plates being juxtaposed with their two uncoated large faces, said two diffusion layers being opposite end faces of said plate body.
 13. An evaporator unit as described in claim 12, wherein said two plates are joined together with their respective large uncoated faces.
 14. An evaporator unit as described in claim 12, wherein said plate body comprises at least one fibrous absorbent plate free from a diffusion layer interposed with its two large faces between and in direct contact with the uncoated large faces of said two end plates.
 15. An evaporator unit as described in claim 12, wherein said frame consists of two half boxes each of which has a window containing a grille, and each of which is mounted about one of said terminal end plates with the window and grille therein spacedly above the diffusion layer of said end plate, and wherein each of said half boxes has a rim disposed about the periphery of the respective end plate and extending beyond the latter toward the other end plate, the rims of both half boxes being sealingly connected with each other.
 16. An evaporator unit as described in claim 15, further comprising protective means comprising two sheets of vapor-impervious material, each of said sheets being sealingly connected to the marginal zones of one of said half boxes about and above said window and grille therein.
 17. An evaporator unit as described in claim 7, wherein said frame is made of said impervious thermoplastic material.
 18. An evaporator unit as described in claim 7, wherein said diffusion layer is made of a thermoplastic polymeric material selected from polyethylene, polypropylene and plasticized polyvinyl chloride.
 19. An evaporator adapted for emitting at room temperature vapors of a volatile active liquid product, comprising a. a plate body having two large end faces at opposite sides thereof and comprising i. at least one fibrous product-absorbing plate and ii. two diffusion layers of polymeric thermoplastic material 10 to 80 Mu thick capable of permitting said product to diffuse therethrough and vapors of said product to evaporate from an outer surface thereof at an effective rate, one of said layers being superimposed on each of said large, principal end faces of said plate body and being intimately joined with its inner face to the adjacent surface of said plate body; each diffusion layer having a marginal portion which extends beyond said plate, the two marginal portions of said diffusion layers being sealed together to form a frame about said plate body b. protective enveloping means of a material impervious to said liquid product and to the vapors of the latter, said protective means being of foiL-shape and tearably and removably laminated on to the outer surface of each of said diffusion layer. 